Notch2-mediated plasticity between marginal zone and follicular B cells

Follicular B (FoB) and marginal zone B (MZB) cells are functionally and spatially distinct mature B cell populations in the spleen, originating from a Notch2-dependent fate decision after splenic influx of immature transitional B cells. In the B cell follicle, a Notch2-signal is provided by DLL-1-expressing fibroblasts. However, it is unclear whether FoB cells, which are in close contact with these DLL-1 expressing fibroblasts, can also differentiate to MZB cells if they receive a Notch2-signal. Here, we show induced Notch2IC-expression in FoB cells re-programs mature FoB cells into bona fide MZB cells as is evident from the surface phenotype, localization, immunological function and transcriptome of these cells. Furthermore, the lineage conversion from FoB to MZB cells occurs in immunocompetent wildtype mice. These findings demonstrate plasticity between mature FoB and MZB cells that can be driven by a singular signaling event, the activation of Notch2. Notch signalling is central to marginal zone B cell development, but it is unclear what path this development takes in vivo. Here the authors use a mouse that lacks these cells to show that transgenic induction of Notch2 is sufficient for development of marginal zone B cells via transdifferentiation from follicular B cells and that this mechanism can occur in wildtype mice.

Automated summary

FoB and MZB cells are functionally distinct mature B cell populations in the spleen, which can be re-programmed through Notch2 activation. The study demonstrates plasticity between these cell types and suggests a potential pathway for MZB cell development in vivo, driven by a singular signaling event.